A method for preparing 5-hydroxymethylfurfural based on a two-phase system one-pot method

Abstract

This invention discloses a one-pot method for preparing 5-hydroxymethylfurfural based on a two-phase system, belonging to the field of comprehensive utilization technology of biomass resources. This invention uses metal phosphates as catalysts combined with organic acids to catalyze the one-pot reaction of straw in a sodium chloride solution-tetrahydrofuran two-phase system. The reaction temperature is 200℃-220℃, and the reaction time is 60-120 min, yielding high-yield 5-hydroxymethylfurfural. The highest yield of 5-hydroxymethylfurfural prepared by this invention can reach 62.88%, which is higher than that of currently reported two-phase reaction systems using lignocellulose as starting material. The process is simple, economical, and environmentally friendly, with low environmental and equipment requirements, and is easily industrialized, possessing high industrialization value.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of biomass resources, specifically relating to a method for preparing 5-hydroxymethylfurfural based on a one-pot method of a two-phase system. Background Technology

[0002] Lignocellulosic biomass is a long-term alternative to fossil fuels and can serve as a raw material for the production of liquid fuels and valuable chemicals. Lignocellulosic biomass is inexpensive, abundant, and widely applicable, making it suitable for the sustainable production of biofuels and chemicals. Straw is one of the major agricultural residues, with low cost and large availability. It is estimated that China produces 6.5 × 10⁶ wheat, rice, and corn straw as agricultural residues annually. 8 Tons of wheat straw are produced, but not effectively utilized. Wheat straw is mainly composed of cellulose (30%-35%), hemicellulose (15%-25%), and lignin (10%-25%). The cellulose and hemicellulose fractions can be hydrolyzed and dehydrated into furan compounds, such as furfural and 5-hydroxymethylfurfural (5-HMF). 5-HMF is a valuable platform compound; due to its wide range of applications, it has been listed by the U.S. Department of Energy as one of the ten most valuable bio-based chemicals. It can be used to replace fossil fuels, providing a biomass-based alternative for the preparation of polymers, pharmaceuticals, pesticides, fragrances, flavorings, macrocyclic and heterocyclic chemicals, etc. In addition, 5-HMF is also a precursor to biodiesel with high calorific value.

[0003] The efficient conversion of cellulose, the main component of lignocellulose biomass, into 5-hydroxymethylfurfural (5-HMF) is a crucial step in utilizing complex biomass as a chemical feedstock. However, this multiphase polymer is insoluble in many common solvents, further complicating the process. Various methods for producing 5-HMF have been developed, such as using non-recyclable toxic heavy metal catalysts or very expensive ionic liquids, but these methods are costly and limit the industrial availability and use of 5-HMF. Due to the recalcitrant nature of lignocellulose, fructose or pretreated sugar solutions are currently commonly used as raw materials for 5-HMF production. However, the high cost of fructose itself limits the use of fructose dehydration for 5-HMF synthesis.

[0004] Patent (CN102050806A) discloses a method for preparing a 5-hydroxymethylfurfural product from lignocellulose, comprising the following steps: mixing an ionic liquid, a metal halide, lignocellulose, and a protic acid uniformly, reacting at a temperature of 201℃~500℃ for 0.01 seconds~60 minutes, and then cooling to -30℃~50℃, with a maximum yield of 5-hydroxyfurfural of 54.5%. This method uses an ionic liquid as the solvent system, which is expensive, environmentally toxic, and has low industrial feasibility.

[0005] Patent (CN110606835A) discloses a method for preparing 5-hydroxymethylfurfural (5-HMF) in the field of biomass carbohydrate resource utilization technology. The method includes the following steps: mixing biomass raw materials, an ionic liquid, and MoCl3 to obtain a reaction solution; the biomass raw materials include monosaccharides, disaccharides, polysaccharides, or larch wood powder; and subjecting the reaction solution to a dehydration reaction under microwave conditions to obtain 5-HMF. This invention uses an ionic liquid as a solvent system, which is environmentally unfriendly. Furthermore, when using larch wood powder as the reaction substrate, the yield of 5-HMF is low, only 1.07%, failing to achieve the goal of high-value utilization of lignocellulose. Summary of the Invention

[0006] To address the problems of high cost, low yield, and environmentally harmful solvent systems in the preparation of 5-hydroxymethylfurfural using lignocellulose biomass in existing technologies, this invention provides a one-pot method for preparing 5-hydroxymethylfurfural based on a two-phase system. This method can obtain 5-hydroxymethylfurfural in high yield, and the steps are simple and economically feasible.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A method for preparing 5-hydroxymethylfurfural using a one-pot method based on a two-phase system includes the following steps:

[0009] (1) Mix lignocellulose biomass, phosphate catalyst, organic acid, sodium chloride, organic solvent and water and add them to the reactor. Heat the reaction system to the reaction temperature and carry out hydrothermal reaction.

[0010] (2) After the reaction is completed, the reaction vessel is cooled to room temperature, the organic phase, aqueous phase and solid residue are separated, and the organic phase and aqueous phase are collected. The product is 5-hydroxymethylfurfural in the organic phase and aqueous phase.

[0011] In step (1), the source of lignocellulose biomass is wheat, rice and corn stalks, which are crushed and passed through a 100-200 mesh powder.

[0012] The organic solvent in step (1) is one of tetrahydrofuran and methyl isobutyl ketone.

[0013] In step (1), the phosphate catalyst is selected from any one of FePO4, CrPO4, AlPO4, Ba3(PO4)2, and Li3PO4.

[0014] In step (1), the organic acid is selected from any one of acetic acid, lactic acid, citric acid, tartaric acid, maleic acid, malic acid, and mandelic acid.

[0015] The mass ratio of the lignocellulose biomass, phosphate catalyst, and organic acid is 1:0.3-0.8:0.25-1.

[0016] The mass ratio of the lignocellulose biomass, sodium chloride, and water is 70–150:300–400:1.

[0017] The volume ratio of the organic solvent to water is 3 to 5:1.

[0018] In step (1), the heating rate of the reaction system is 5-15℃ / min, the reaction temperature is 200-220℃, and the reaction time is 60-120min.

[0019] In step (1), the reaction system is carried out in an inert atmosphere, and the pressure of the inert atmosphere in the reactor is 0.5-2 MPa; more preferably, in step (1), the reaction system is carried out in a nitrogen atmosphere of 1.5 MPa.

[0020] The cooling process in step (2) involves first naturally cooling the temperature to below 100°C, and then cooling it to room temperature using an ice water bath.

[0021] The most crucial step in the one-pot conversion of lignocellulose is the depolymerization of cellulose into corresponding monomeric sugars under the catalysis of biomass acids, followed by isomerization into fructose. Fructose then undergoes dehydration to produce 5-hydroxymethylfurfural. The depolymerization of cellulose in lignocellulose is catalyzed by protic acid H... + The cleavage of the 1,4-glycosidic bond in cellulose is catalyzed, and the hydrolysis of phosphate catalysts at high temperatures can provide H₂. + Dissolved phosphate acts as a Lewis acid, promoting the isomerization of glucose to fructose. The phosphate catalyst then pairs with organic acids as... The acid, in the same reaction mixture, dehydrates the resulting fructose to 5-hydroxymethylfurfural. This combination shows improved selectivity in the overall conversion of glucose to 5-hydroxymethylfurfural, effectively increasing the yield of 5-hydroxymethylfurfural.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Compared with other traditional two-step methods for preparing 5-hydroxymethylfurfural, the present invention uses a one-pot method to prepare 5-hydroxymethylfurfural. The reaction steps are simple, the yield is high, and the maximum yield can reach 62.88%, which is beneficial to the high-value conversion of lignocellulose biomass.

[0024] (2) The raw materials of the present invention are widely available and inexpensive, and the catalysts and co-catalysts are also easy to obtain. It can create high value at a low cost and has excellent prospects in large-scale industrial production.

[0025] (3) This invention creatively incorporates organic acids, making the organic acid pairing, based on the fact that metal phosphates are Lewis acids, a result in the addition of organic acids. Acid promotes the dehydration of fructose into 5-hydroxymethylfurfural, which is beneficial to the yield of 5-hydroxymethylfurfural.

[0026] (4) This invention does not use ionic liquids as solvent systems in traditional methods, which is relatively more environmentally friendly. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0030] In Examples 1-5 and Comparative Examples 1-2, the lignocellulose biomass was wheat straw that had been crushed and passed through a 200-mesh sieve.

[0031] Example 1

[0032] Weigh 0.4 g of lignocellulose biomass, 0.28 g of FePO4, 0.2 g of mandelic acid, 1.4 g of NaCl, 20 ml of THF, and 4 ml of water into a 50 ml Hastelloy autoclave. Heat at 200 °C for 90 min at 500 rpm, with a heating rate of 10 °C / min. The N2 pressure in the autoclave is 1 MPa. After the reaction is complete, allow the autoclave to cool to below 100 °C, then cool to below 30 °C using an ice-water bath. Collect the organic and aqueous phases, and determine the yield of 5-hydroxymethylfurfural by HPLC.

[0033] Example 2

[0034] Weigh 0.4 g of lignocellulose biomass, 0.12 g of AlPO4, 0.2 g of malic acid, 1.2 g of NaCl, 16 ml of methyl isobutyl ketone, and 4 ml of water into a 50 ml Hastelloy autoclave. Heat at 220 °C for 60 min at a rotation speed of 500 rpm and a heating rate of 10 °C / min. The N2 pressure in the autoclave is 0.5 MPa. After the reaction is complete, allow the autoclave to cool to below 100 °C, then cool to below 30 °C using an ice-water bath. Collect the organic and aqueous phases, and determine the yield of 5-hydroxymethylfurfural by HPLC.

[0035] Example 3

[0036] Weigh 0.4 g of lignocellulose biomass, 0.2 g of Ba3(PO4)2, 0.2 g of acetic acid, 1.6 g of NaCl, 12 ml of THF, and 4 ml of water into a 50 ml Hastelloy autoclave. Heat at 220 °C for 120 min at a rotation speed of 500 rpm and a heating rate of 10 °C / min. The N2 pressure in the autoclave is 1.5 MPa. After the reaction is complete, cool the autoclave to below 100 °C and then cool it to below 30 °C using an ice-water bath. Collect the organic and aqueous phases, and determine the yield of 5-hydroxymethylfurfural by HPLC.

[0037] Example 4

[0038] Weigh 0.21g of lignocellulose biomass, 0.126g of Li3PO4, 0.21g of tartaric acid, 1.28g of NaCl, 20ml of methyl isobutyl ketone, and 4ml of water into a 50ml Hastelloy autoclave. Heat at 210℃ for 60min at 500rpm, with a heating rate of 10℃ / min. The N2 pressure in the autoclave is 2MPa. After the reaction is complete, allow the autoclave to cool to below 100℃, then cool to below 30℃ using an ice-water bath. Collect the organic and aqueous phases, and determine the yield of 5-hydroxymethylfurfural by HPLC.

[0039] Example 5

[0040] Weigh 0.6 g of lignocellulose biomass, 0.48 g of FePO4, 0.15 g of citric acid, 1.44 g of NaCl, 16 ml of THF, and 4 ml of water into a 50 ml Hastelloy autoclave. Heat at 200 °C for 90 min at 500 rpm, with a heating rate of 10 °C / min. The N2 pressure in the autoclave is 1 MPa. After the reaction is complete, allow the autoclave to cool to below 100 °C, then cool to below 30 °C using an ice-water bath. Collect the organic and aqueous phases, and determine the yield of 5-hydroxymethylfurfural by HPLC.

[0041] Comparative Example 1

[0042] This comparative example is based on the setup of Example 1, except that no organic acid was added, while all other conditions are the same as in Example 1.

[0043] Weigh 0.4 g of lignocellulose biomass, 0.28 g of FePO4, 1.4 g of NaCl, 20 ml of THF, and 4 ml of water into a 50 ml Hastelloy autoclave. Heat at 200 °C for 90 min at a rotation speed of 500 rpm and a heating rate of 10 °C / min. The N2 pressure in the autoclave is 1 MPa. After the reaction is complete, allow the autoclave to cool to below 100 °C, then cool to below 30 °C using an ice-water bath. Collect the organic and aqueous phases, and determine the yield of 5-hydroxymethylfurfural by HPLC.

[0044] Comparative Example 2

[0045] This comparative example is based on the settings of Example 1, except that the reaction temperature is lowered to 180°C, while all other conditions are the same as in Example 1.

[0046] Weigh 0.4 g of lignocellulose biomass, 0.28 g of FePO4, 0.2 g of mandelic acid, 1.4 g of NaCl, 20 ml of THF, and 4 ml of water into a 50 ml Hastelloy autoclave. Heat at 180 °C for 90 min at a rotation speed of 500 rpm and a heating rate of 10 °C / min. The N2 pressure in the autoclave is 1 MPa. After the reaction is complete, allow the autoclave to cool to below 100 °C, then cool to below 30 °C using an ice-water bath. Collect the organic and aqueous phases, and determine the yield of 5-hydroxymethylfurfural by HPLC.

[0047] Performance testing

[0048] The 5-hydroxymethylfurfural content of the products collected in Examples 1-5 and Comparative Examples 1-2 was tested. The 5-hydroxymethylfurfural content in the products was determined using an Agilent 1260 high-performance liquid chromatograph, and the external standard method was used for quantification. The high-performance liquid chromatography detection conditions were: Supersil ODS2, mobile phase CH3OH:H2O = 60:40, flow rate: 0.5 mL / min, column temperature: 30℃, detector: ultraviolet (UV), detection wavelength: 280 nm.

[0049] The cellulose, hemicellulose, and lignin contents of this lignocellulose biomass are shown in Table 1 below:

[0050] Table 1. Percentage content of various components in lignocellulose biomass

[0051]

[0052] The formula for calculating the yield of 5-hydroxymethylfurfural in the example is:

[0053]

[0054] In the formula HMF orgV represents the concentration of 5-hydroxymethylfurfural in the organic phase. org HMF is the volume of the organic phase. aq V represents the concentration of 5-hydroxymethylfurfural in the aqueous phase. aq Let be the volume of the aqueous phase.

[0055] Table 1 below shows the molar yield test results of 5-hydroxymethylfurfural in the final products of Examples 1-5 and Comparative Examples 1-2.

[0056] Table 1. Yields of 5-hydroxymethylfurfural in Examples 1-5 and Comparative Examples 1-2

[0057] Serial Number 5-Hydroxymethylfurfural mol% Example 1 61.90 Example 2 59.95 Example 3 62.88 Example 4 58.38 Example 5 60.06 Comparative Example 1 52.7 Comparative Example 2 16.2

[0058] As shown in Table 1, the yield of 5-hydroxymethylfurfural in Examples 1-5 was 58%, with the yield in Example 3 reaching 62.88%.

[0059] Comparing Example 1 with Comparative Example 1, the addition of organic acid effectively increases the yield of 5-hydroxymethylfurfural. From Example 1 and Comparative Example 2, it can be seen that temperature is crucial to the yield of 5-hydroxymethylfurfural; when the temperature is lowered to 180°C, with other conditions unchanged, the yield only reaches 16.2%. Only by simultaneously adjusting both temperature and organic acid—two important elements—can efficient conversion of wheat straw be achieved to obtain a high yield of 5-hydroxymethylfurfural.

[0060] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing 5-hydroxymethylfurfural in a one-pot process based on a two-phase system, characterized in that, Includes the following steps: Lignocellulose biomass, phosphate catalyst, organic acid, sodium chloride, organic solvent and water are mixed and added to a reactor. The reaction system is heated to the reaction temperature to carry out a hydrothermal reaction. After the reaction is complete, the reaction vessel is cooled to room temperature. The organic phase, aqueous phase, and solid residue are separated. The organic phase and aqueous phase are collected, and the product is 5-hydroxymethylfurfural in the organic phase and aqueous phase. In step (1), the organic acid is selected from any one of acetic acid, lactic acid, citric acid, tartaric acid, maleic acid, malic acid, and mandelic acid. In step (1), the phosphate catalyst is selected from any one of FePO4, CrPO4, AlPO4, Ba3(PO4)2, and Li3PO4; The reaction temperature in step (1) is 200–220°C; The mass ratio of the lignocellulose biomass, phosphate catalyst, and organic acid is 1:0.3-0.8:0.25-1.

2. The method for preparing 5-hydroxymethylfurfural based on a one-pot method in a two-phase system according to claim 1, characterized in that, In step (1), the source of lignocellulose biomass is wheat, rice and corn straw that has been crushed and passed through a 100-200 mesh powder.

3. The method for preparing 5-hydroxymethylfurfural based on a one-pot method in a two-phase system according to claim 1, characterized in that, The organic solvent in step (1) is one of tetrahydrofuran and methyl isobutyl ketone.

4. The method for preparing 5-hydroxymethylfurfural based on a one-pot method in a two-phase system according to claim 1, characterized in that, The volume ratio of the organic solvent to water is 3 to 5:

1.

5. The method for preparing 5-hydroxymethylfurfural based on a one-pot method in a two-phase system according to claim 1, characterized in that, In step (1), the heating rate of the reaction system is 5-15℃ / min, and the reaction time is 60-120min.

6. The method for preparing 5-hydroxymethylfurfural based on a one-pot method in a two-phase system according to claim 1, characterized in that, In step (1), the reaction system is carried out in an inert atmosphere, and the pressure of the inert atmosphere in the reactor is 0.5-2 MPa.

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